Compact materials handling devices are known that are operated by compressed air. Representative of these materials handling devices are the ones marketed under the brand name EasyMover. One version of the EasyMover device is disclosed in U.S. Pat. No. 4,582,154. A drawback of these compressed air powered devices is that they are required to be “tethered” in view that the compressed air needs to be fed to them typically through a ⅜″ to ½″ air line connected to a compressed air power source. These compressed air powered devices, nonetheless, do have certain advantages, which include: (1) they are very mobile and small in size yet can generate significant amounts of torque; (2) their compact size allows them to be fitted under most heavy rollable loads that require moving so that the weight of the load can provide the downward force on the driven wheel(s) of the power handling device to provide the traction required to move the load; and (3) they do not suffer any downtime in that the provided compressed air is always available and they are always connected to the compressed air so they can operate without interruption.
However, these compressed air powered devices also suffer from certain disadvantages, which include: (1) the requirement for compressed air limits use of these devices to locations and applications that have the required compressor available; (2) the requirement that the devices always be tethered by an air line can also severely restrict their use in many locations and applications; for example, if it is necessary to move a load over a long distance the air line becomes too cumbersome to manipulate, and for yard and/or outdoor applications the air line becomes unrealistic; (3) the volume of compressed air that can be supplied through an air line decreases as the length of the air line increases; accordingly, it is generally not feasible to operate the device through much more than 30 to 50 feet of air line, due to the reduced volume of air that can be supplied; and (4) to achieve their compact size these devices utilize a very compact, but very inefficient rotary vane style of pneumatic motor (having approximately 30% efficiency), that results in a very high consumption of compressed air. This high volume consumption precludes any possibility of moving the energy store to the unit itself (such as connecting refillable or quick-change compressed air cylinders to the device) as they would need to be very large to provide anything more than about a minute of continuous operation. In addition there is an unacceptable energy cost of operating at this level of inefficiency.
Alternatively, substantially less compact materials handling devices are available which are battery powered and thus are not tethered. Representative of these materials handling devices are the ones marketed under the brand names MasterMover, Nustar/PowerPusher and Electrodrive. Each of these devices have substantially similar designs that typically utilize an electric motor, a high reduction (typically worm style) gearbox and one or more 12-volt deep discharge sealed lead acid (SLA) batteries as their power source. While such battery powered devices have the benefit of being untethered, providing a greater degree of mobility and range of operation than the pneumatic powered devices, while still being capable of generating significant amounts of torque, they lose the key benefits of the pneumatic powered devices in that the battery powered devices: (1) are significantly larger and heavier than the pneumatic devices which reduces the ease of use, maneuverability, etc., of the battery powered devices; (2) in being significantly larger, typically are not locatable under the load being moved and so oftentimes require an auxiliary downward force or cumbersome geometry to provide the necessary downward force on the drive rollers (to provide the roller traction) to move the load; and (3) typically require downtime for recharging of the onboard batteries which can limit their functionality in high duty cycle applications.
Consequently, a need still exists for an innovative device which will avoid the aforementioned problems in the prior art with respect to pneumatic and battery powered high torque devices without introducing any new problems in place thereof.